In modern aircraft, it is of critical importance to provide accurate and timely information to the pilot to facilitate effective flight management. The nature of the pilot's various tasks determines the general types of data which must be made available to the pilot. In a display system it is important to provide each type of data in a form best suited for that data type. Preferably, each form of data is presented in a manner suited for use such that extensive mental processing is not required before information can be used by the pilot. Thus, in a properly configured display, more information can be presented to the pilot and utilized with less effort in mental processing, and can be expected to translate into fewer pilot errors.
Many modern aircraft displays utilize computer generated electronic images to offer significant advances in their ability to provide a wide range of information to the pilot. One type of instrument that is commonly included in modern aircraft displays are lateral acceleration indicators. Lateral acceleration indicators, sometimes also referred to as “slip-skid” indicators or simply slip indicators, are used to provide visual indication of lateral mistrim to the pilot.
Lateral mistrim, sometimes referred to as uncoordinated flight, slipping or skidding, occurs when the tail of the aircraft is not properly situated behind the front of the aircraft. Lateral mistrim is undesirable in that it is generally inefficient, and can thus result in excessive fuel consumption. Additionally, lateral mistrim can make the flight uncomfortable. Finally, lateral mistrim can be an indication of a greater problem such as a loss of power in an engine, and can itself result in a loss of control during certain low speed maneuvers. For all these reasons, it is strongly desirable to provide a good visual indication of lateral mistrim to the pilot.
Early lateral acceleration indicators were relatively simple mechanical devices that used a ball in a concave glass enclosure. During coordinated flight, the ball remained in the center of the glass enclosure. When lateral mistrim occurred, the ball moved from the center and thus provided visual indication to the pilot. While these early mechanical indicators provided effective visual representation of mistrim, they were not compatible with modern electronic displays used in new systems.
There have been several attempts at incorporating lateral acceleration indicators into electronic displays. These electronic indicators have suffered from some limitations, namely, the have not provided both visual indication of small amounts of lateral mistrim and a strong visual indication for large amounts of lateral mistrim.
Thus, what is needed is an improved electronic lateral acceleration indicator that provides the ability to indicate small amounts of lateral mistrim and also provides strong visual indication when large amounts of lateral mistrim are occurring.